1. Technical Field
The present invention relates to a shear force detection device to detect stress in a shear direction, a tactile sensor including the shear force detection device and a grasping apparatus including the tactile sensor.
2. Related Art
A known grasping apparatus uses a robot arm, robot hand, robot manipulator or the like to grasp and lift an object whose weight and friction coefficient are unknown. To grasp the object without damaging or dropping the object, it is necessary to detect a force (positive pressure) acting in a direction perpendicular to the grasping surface and a force (shear force) acting in a surface direction (shear direction) of the grasping surface. A known sensor is used to detect these forces (see, for example, JP-A-2006-208248).
The tactile sensor disclosed in JP-A-2006-208248 has a cantilever structural body extending from an edge portion of an opening opened in a sensor substrate, and this structural body includes a plate-shaped sensitive part, and a hinge part to couple the sensitive part and the sensor substrate. A conductive magnetic film is formed on the sensitive part of the structural body, a piezoresistive film is formed on the hinge part, and the conductive magnetic film and the piezoresistive film are electrically connected. Further, an electrode is provided on the hinge part, and when the hinge part is bent by pressure, a current generated in the piezoresistance of the hinge part flows from the electrode. In this tactile sensor, plural such structural bodies are formed on the sensor substrate, some of these structural bodies are erected with respect to the sensor substrate, and the others are kept in parallel to the sensor substrate. Still further, an elastic body is provided on the sensor substrate, and the erected structural body is embedded in the elastic body. As such, the erected structural body can measure the shear force, and the structural body parallel to the substrate surface can measure the positive pressure.
In order to manufacture the tactile sensor as stated above, a P-type resistance region is formed in the surface of the sensor substrate by a heat diffusion method or the like, and a conductive magnetic layer is patterned by sputtering. Then, the conductive magnetic layer is used as a mask, an impurity layer and a Si layer are removed by ion etching, and further, the conductive magnetic film formed on the surface of the hinge part is etched. Thereafter, an opening part for shaping the outer shape of the structural body is formed by reactive ion etching or the like. Some of the plural structural bodies are erected by applying a magnetic field from the rear side of the sensor substrate, and the tactile sensor is manufactured.
The tactile sensor as disclosed in JP-A-2006-208248 has a complicated three-dimensional structure in which the cantilever structural body is erected, and the manufacturing thereof includes a complicated manufacturing process in which the magnetic field is applied to bend the cantilever structural body. Accordingly, the productivity is poor.